Dr. Helena Russell wages a desperate fight for the life of a girl whose husband has visions of Alpha being destroyed by fire...visions made all the more ominous when a fire storm sweeps towards the moon. ITC summary

Normal fire cannot burn in space, but they could be colliding with a protostar or dense gas cloud, the gravity of which would heat up the gases. It would also create the shockwaves and explosions seen.

The first artificial heart was implanted in a patient in 1983. Complete mechanical hearts can damage red blood cells and are vulnerable to infection. More success has been found with small titanium pumps sewn directly into the left ventricle, a type that was used for the first successful long term artificial heart patient in 2000. The first entirely internal artificial heart (with no leads or pumps) was implanted in 2001. The box-like device in this episode looks more like a pacemaker than a blood pump. The operation and post operative care look nothing like modern medical procedures (especially putting a man covered in blood and dirt next to a patient recovering from a major operation).

The Moon's surface temperature is said to rise to 40 Centigrade. This is a warm day on Earth- the normal temperatures on the Moon in Earth orbit reach 120 Centigrade.

The catacombs are also seen but not so named in Mark Of Archanon. Most caves on Earth are formed by water, which is not present on the moon. They are too small and uneven to be excavated by modern mining methods. They may be lava tubes. These are formed as the surface lava cools and insulates lava flowing in channels under it. The best known examples on Earth are in Hawaii, and the Craters Of The Moon National Monument, Idaho, USA. They can meander like a river, and typically have flat floors and roofs. As there is no geothermal heat on the Moon the air would freeze against the rock walls. The first evidence of lava tubes on the moon was discovered in 2010.

Cats cannot see in pitch dark. They can see in much poorer light than humans as their eyes have a reflective layer behind the retina (the tapetum lucidum) which bounces back light to the optic nerve (this also makes the eyes of cats and other nocturnal animals glow in the dark). But there is no light at all in the caves. Only radar-like sound would allow a creature to navigate in a cave, so Michael Butterworth's adaption of the story had Maya change into a bat-like alien.